Certain mechanisms, such as refrigerant compressors or the like, employ drive units adapted for intermittent activation depending on the requirements of the mechanism. To control activation, these mechanisms usually employ a clutch plate secured to a hub mounted on the mechanism's drive shaft which may be engaged with a continuously driven rotating member by activation of an electromagnet mounted on the mechanism housing. To permit continuous driving of the rotating member and for compactness, the rotating member is positioned coaxially with the drive shaft on a spindle formed by an extended portion of the mechanism housing. A roller bearing is disposed between the spindle and the rotating member and carries the rotating member on the spindle. The electromagnet, rotating member, and clutch plate are juxtapositioned so that when the electromagnet is energized, the rotating member is magnetized, attracting the clutch plate which drives the mechanism's drive shaft.
In vehicular installations, these mechanisms are often required to operate in contaminated environments laden with dust, dirt and moisture, and are subjected to high temperatures, all of which are detrimental to bearing and seal life. It is also believed that magnetization of the bearing, when the mechanism is being driven, attracts certain foreign particles. Although the bearings used to mount the rotating member on the spindle are conventionally of the sealed type, having lip-type seals mounted between the inner and outer races on both sides of the bearing, the bearing faces are exposed to several paths or passages which allow contaminants to pack against the bearing faces and lip-type seals. Over a period of time, the environmental factors and forces within the mechanism cause the contaminants to lift the bearing seals from their seats permitting the entrance of foreign matter into the bearing. This results in failure of the bearing and the need to frequently service the drive unit.
U.S. Pat. No. 3,743,068 teaches a dual seal arrangement including a seal structure at the free end of the stationary spindle comprising a seal support and bearing retainer cup carried by the rotating member and having a felt seal bonded thereto and held in sealing relationship with the free end of the stationary spindle. Due to the location of such seal structure at the free end of the spindle, it receives the greatest exposure to contaminated environments and it has been found that dust, dirt and moisture tend to migrate through the sealing relationship between the parts, although at a greatly reduced rate, to eventually produce a detrimental effect on the bearing.
It is an object of this invention to reduce the migration of contaminants through the seal arrangement while at the same time imposing only minimal resistance on the rotational components of the mechanism and retaining lubricant within the bearing.